There is consensus that the development and progression of myopia in children are determined by both environmental and inherited factors, although their mechanisms and the amount of genetic/environmental interaction remain poorly understood. Most studies of myopia, both in human and animal models, have investigated the onset of myopia. Much less is known about the time course of progression and eventual stabilization of myopia and the factors that may influence the final amount and the age of stabilization. The Correction of Myopia Evaluation Trial (COMET), a multi-center, randomized clinical trial designed to evaluate whether progressive addition lenses (PALs) slow the progression of myopia compared to single vision lenses (SVLs), enrolled 469 myopic children who have been carefully followed with annual standardized measurements of myopia by cycloplegic autorefraction and axial length over a 3-year period. Retention has been excellent, with 98.5% of children completing 3 year follow-up visits. Four year follow up visits will be completed in October, 2002, and soon after that the study design will shift from a clinical trial to a longitudinal investigation. The COMET cohort provides a unique opportunity to characterize myopia progression and how it is influenced by factors identified in the first phase of COMET as well as new data on familial myopia, including genetic analyses. Better understanding of the factors predictive of myopia progression and stabilization also will help guide selection and timing of interventions as well as target those groups that may benefit most from treatment. This application seeks to accomplish the following aims by collecting data from COMET children for an additional 5 years. The specific aims in COMET: Phase II are: Aim 1: To develop predictive models and identify factors that characterize changes over a 9 - year period in myopia and axial length in the cohort of children who have participated in the Correction of Myopia Evaluation Trial. Aim 2: To complete ascertainment of the pedigrees of COMET families and to conduct studies designed to investigate genetic loci for juvenile-onset myopia, beginning with those previously identified for high myopia. Aim 3: To evaluate the long term effect (i.e., beyond 3 years) of having worn either PALs or single vision lenses (SVLs) for 3 years.